Bonding method is a well-known representative method for fabricating an SOI wafer (Silicon on Insulator) which comprises an insulating layer such as a silicon oxide film, and a silicon single crystal layer formed as being stacked thereon. Among others, ion implantation delamination method, so-called Smart Cut® Process (registered trademark) has been attracting a public attention, in which a silicon single crystal is implanted with ions and then annealed, so as to partially break the crystal lattice of silicon at the layer where the implanted ions reside, to thereby form an SOI layer.
In the Smart Cut Process® shown in FIG. 1, a bond wafer 31 having an ion implanted layer 41 formed therein and a base wafer 32 on which an SOI layer 40 is to be formed later are annealed as being closely contacted with each other while placing in between an insulating film 33 such as an oxide film which composes the surficial portion of the bonding-side main surface of at least either one of the wafers. By the annealing, the surficial portion of the bonding-side main surface of the bond wafer 31 is delaminated at the ion implanted layer 41 so as to form the SOI layer 40, and is bonded to the base wafer 32 to thereby obtain an SOI wafer 39.
In the above-described fabrication process, a conventional method of separating a residual wafer 38, which is a residue of the bond wafer 31, from the SOI wafer 39 was proceeded as described below. As shown in FIG. 7, each of holding grooves 30a of a boat 30 drawn out of a furnace after the annealing holds the residual wafer 38 and the SOI wafer 39 as being stacked with each other. The residual wafer 38 or the SOI wafer 39 is recovered while being chucked by a vacuum chuck 36 on the back surface thereof.
Use of the vacuum chuck as shown in FIG. 7, however, makes it difficult to separate both wafers while keeping a parallel positional relation so as to avoid contact therebetween. Any accidental friction between both wafers to be separated may result in scratching on the surface. The scratching in particular on the SOI wafer is undesirable because it may result in a lowered yield ratio.
It is therefore a subject of this invention to provide a method of fabricating an SOI wafer without causing scratches on the wafer surface, and a wafer separation jig used therefor.